1. Field of the Invention
The present invention relates to wireless communications, and more particularly, to a method and apparatus for transmitting data in a wireless communication system.
2. Related Art
The institute of electrical and electronics engineers (IEEE) 802.16e standard was adopted in 2007 as a sixth standard for international mobile telecommunication (IMT)-2000 in the name of ‘WMAN-OFDMA TDD’ by the ITU-radio communication sector (ITU-R) which is one of sectors of the international telecommunication union (ITU). An IMT-advanced system has been prepared by the ITU-R as a next generation (i.e., 4th generation) mobile communication standard following the IMT-2000. It was determined by the IEEE 802.16 working group (WG) to conduct the 802.16m project for the purpose of creating an amendment standard of the existing IEEE 802.16e as a standard for the IMT-advanced system. As can be seen in the purpose above, the 802.16m standard has two aspects, that is, continuity from the past (i.e., the amendment of the existing 802.16e standard) and continuity to the future (i.e., the standard for the next generation IMT-advanced system). Therefore, the 802.16m standard needs to satisfy all requirements for the IMT-advanced system while maintaining compatibility with a mobile WiMAX system conforming to the 802.16e standard.
There is ongoing development on the institute of electrical and electronics engineers (IEEE) 802.16p standard optimized for machine-to-machine (M2M) communication based on the IEEE 802.16e standard and the IEEE 802.16m standard. The M2M communication can be defined as an information exchange performed between a subscriber station and a server or between subscriber stations in a core network without any human interaction. In the IEEE 802.16p standard, there is an ongoing discussion on enhancement of medium access control (MAC) of the IEEE 802.16 standard and a minimum change of an orthogonal frequency division multiple access (OFDMA) physical layer (PHY) in licensed bands. Due to the discussion on the IEEE 802.16p standard, a wide area wireless coverage is required in the licensed band, and a scope of applying automated M2M communication can be increased for an observation and control purpose.
When accessing a network, requirements demanded by many M2M applications are significantly different from requirements for human-initiated or human-controlled network access. The M2M application can include vehicular telematics, healthcare monitoring of bio-sensors, remote maintenance and control, smart metering, an automated service of a consumer device, etc. The requirements of the M2M application can include very lower power consumption, larger numbers of devices, short burst transmission, device tampering detection and reporting, improved device authentication, etc.
Similarly to the IEEE 802.16m standard, the IEEE 802.16p standard can also support transmission of a short message service (SMS). The M2M device is characterized in short burst transmission, and thus effective SMS transmission of the M2M device is required. In addition, since it is expected that the M2M device primarily operates in an idle mode, there is a need for an effective method for transmitting the SMS while decreasing a signaling overhead in the idle mode.